1. Field of the Invention
This invention pertains to a Hall element electronic device with an InAs channel which has high sensitivity and enhanced stability over a large temperature range and which can sense electrical and magnetic fields.
2. Description of Related Art
Hall elements using III-V semiconductor materials have widespread use for a variety of military and commercial applications. They are mostly commonly used as magnetic field sensors in small DC brushless motors found in electronic consumer equipment such as video cassette recorders, personal computers, and compact disk drives. They also are used for position, tilt-level, pressure and thickness sensing as well as in tachometers, compasses, magnetizers, and electronic measurement equipment used to detect current, voltage, power, frequency, and magnetic field. They are also used in the non-destructive evaluation of materials to detect hair line cracks in metals for such applications as wing and fuselage inspection.
In 1995, approximately one billion Hall sensors were manufactured worldwide. The market for such sensors is growing rapidly, and many new applications for the contactless sensors are expected in the future because they can detect static as well as variable magnetic and electric fields.
Hall sensors using InSb material are the most prevalent Hall elements used today compared to those which are composed of GaAs or InAs material. The attractive features of the InSb Hall sensors are high sensitivity, low power consumption, and small offset voltage. Due to the narrow band gap of InSb, however, these Hall sensors have a large temperature dependance which limits their use to near room temperature applications.
InAs Hall sensors are more stable over a wider temperature range, and thus are needed for many present and future applications which have more severe operating conditions. For example, automotive sensors located in the engine compartment or outside the body frame are required to operate over a temperature range from -40.degree. C. to 150.degree. C. Compared to InSb Hall sensors, InAs Hall sensors also have a better stability against pulse voltage noise, lower offset voltage drift, and lower noise properties which enable sensing of smaller magnetic fields.
To meet the demand for improved performance, considerable effort has focused on the development of advanced material growth and device fabrication technology using the AlSb/InAs materials system. AlSb/InAs Hall sensors use AlSb/InAs heterojunctions to form an InAs deep quantum well. This approach is preferred over InAs material obtained using conventional thin film technology due to the attractive features of this heterojunction material system, which include high electron mobility and velocity, high sheet charge density, good carrier confinement, and enhanced design flexibility.
Accurately controlled "band-gap engineered" layer designs with feature sizes on the atomic scale can be used to exploit desirable quantum confinement effects within the structure. As a result of these unique and substantially improved material properties, AlSb/InAs-based quantum well Hall elements are particularly suitable for present and future sensor applications.
To realize high sensitivity in a Hall element, a high electron mobility is required for the InAs layer. Compared to GaAs Hall elements, the lower electron effective mass of InAs gives this material system a significant advantage in the room-temperature mobility which can be achieved for a given sheet charge density.
Compared to other III-V semiconductor material systems, such as GaAs and InP, AlSb/InAs material growth and device fabrication technology is relatively immature. However, recent progress in these areas has enabled antimonide-based devices to be produced with higher mobilities, higher sheet carrier concentrations, lower contact resistance, and improved overall performance. As an example, AlSb/InAs high-electron mobility transistors (HEMTs) have recently been fabricated which exhibit high frequency performance which constitutes the state-of-the-art at low drain voltage.